Method and apparatus for equalizing longitudinal variations in the running of a web under tension

ABSTRACT

This invention relates to a method and apparatus for equalizing longitudinal variations in the running of a web under tension, wherein the web is passed over a support therefor which is at least partially oscillatable in accordance with the longitudinal variations of the web and the oscillatable portions of which are of such low inertia that they oscillate in phase with the oscillating web, and the non-oscillating portions of the web are supported.

United States Patent [191 Schmidt et al.

[ Feb. 5, 1974 METHOD AND APPARATUS FOR EQUALIZING LONGITUDINAL VARIATIONS IN THE RUNNING OF A WEB UNDER TENSION [75] Inventors: Willi J; Schmidt, Hahn/Taunus;

Wolfgang Kornelli; Eberhard Werner, both of Wiesbaden-Biebrich, all of Germany [73'] Assignee: Kalle Aktienges'ellschaft,

Wiesbaden-Biebrich, Germany 22 Filed: oc.'22, 1970 21 Appl. No.2 83,218

Related US. Application Data [63] Continuation-impart of Ser. No. 825,658, May 19,

1969, abandoned.

[30] Foreign Application Priority Data May 21,1968 Germany 17743 10 52 us. cl. 226/195, 242/753 51 Int. Cl B65h 23/00 [58] Field of Search 242/55, 75.2, 75.3; 226/1, 226/10, 15, 2l,191,195,186,175,168

[56] l f References Cited.

UNITED STATES PATENTS 2,287,768 6/1942 Eckstein 226/1 Johnson 226/195X 1,617,560 2/1927 Aldrich 226/168 Primary Examiner-Richard A. Schacher Attorney, Agent, or Firm-James E. Bryan [57] ABSTRACT This invention relates to a method and apparatus for equalizing longitudinal variations in the running of a I web under tension, wherein the web is passed over a support therefor which is at least partially oscillatable in accordance with the longitudinal'variations of the web and the oscillatable portions of which are' of such low inertia that they oscillate in phase with the oscillating web, and the non-oscillating portions of the web are supported.

5 Claims, 7 Drawing Figures PATENTEB 5 74 ATTORNEYS 1 METHOD AND APPARATUS FOR EQUALIZING LONGITUDINAL VARIATIONS IN THE RUNNING OF A WEB UNDER TENSION roller which, if necessary, may be provided with a compensating weight and is capable of following the longitudinal variations by moving about the point of suspension, web tension being maintained constant in this way. I This principle is widelyknown and applied in many different ways. A prerequisite for the satisfactory functioning of such rollers is that the roller should be capable of following the longitudinal variations or oscillation of the web. These rollers may be mountedhorizontally or vertically, or in an intermediate position. To enable such arrangements to function properly, it is necessary to consider the ratio of the frequency of the oscillations concerned (longitudinal variations) to the mass of the roller which is to participate in the movement. It follows that there must be a limit beyond which this type of roller can no longer follow the web oscillations. Thus, phase-displacements may be created which make the intended equalization impossible.

in a similar arrangement, the equalizing roller does not execute a swinging movement, but moves in inclined guides and is again provided with balancing weights or, alternatively, suspended from springs. It executes an upward and downward reciprocating movement, and the web partially envelops the roller. The same disadvantages, e.g., phase-displacement, also I occur inthis type of arrangement.

It also has been proposed to pass a web subject to oscillations overa roller provided with a deformable coating. Equalization of the longitudinal variationsis .here achieved inthat the surface is compressed during peak tensions and expands again during the troughs. While this device is capable of dealing with considerably higher frequencies, the longitudinal variations that it can'equalize are very small, usually of the order of a few millimeters. It also is necessary to operate with increased web tension, in order to obtain the desired degree of deformation of the roller surface. This method, therefore, is particularly unsuitable for the equaliztion of longitudinal variations in thin, sensitive webs. Other devices are known for the substantially inertiafree equalization of longitudinal web oscillations and- /or length variations. Very narrow and, at the same time, suitably stiff webs can be drawn into a shaft maintained under reduced pressure, thereby producing a loop in the web from which variations in tension can be compensated. The upper and lower limits of the loop may be determined by a photocell device. In other known arrangements, vacuum devices are included which ensure a loop of adequate size. However, the applicability of such systems is limited. On the other 2 hand, only striplike webs can be controlled and, on the other, an enclosed apparatus is necessary.

The present invention provides a method for equalizing longitudinal variations, especially short-phase longitudinal variations, and/or longitudinal web oscillations in the running of a web under tension, wherein the web is passed over a support therefor which is at least partially oscillatable in accordance with the longitudinal variations of the web and the oscillatable portions of which are of such a low inertia that they oscillate in phase with the oscillating web, and the non-oscillating portions of the web are supported.

This substantially inertia-free method for equalizing longitudinal variations, especially short-phase longitudinal variations and/or longitudinal web oscillations, is equally suitable for webs subjected to high or low tensile stress-and is irrespective of the sensitivity of the web.

In this method the total forces resulting from web tension are absorbed by the mounting or carrier on which the support rests and the oscillatable portion of the support has 'aninertia so low that it can follow the web oscillations in phase. This is possible even at frequencies of up to about 50 oscillations'per second.

The support, which is capable of oscillation as indicated, is either fixed to the carrierin a manner allowing of such oscillation, or, preferably, is capable of movement in the direction of travel of the webin contact with it. Movement of the support preferably takes place at the same surface speed as the speed of .the web. The carrier is either fixed, or, if separate from the support, may be movable, preferably. in synchronism with the support.

Along a web path within which longitudinal variations are to be equalized, the support and the carrier may be mounted at any desired point, for example in contact with the outer winding of a roll of web on a supply or take-up core.

The method of the invention is able to deal with webs of cellulose or plastic sheeting of any kind, which may have been surface-treated or coated. The method is likewise applicable to paper or textile webs, metal foils and other sheet material or coated material of any de- The tensioned web is brought into contact with the a surface of the described support and is-conducted in such a way that, as the web tension varies, the support surface is deformed in accordance with the longitudinal Y variation of the web. The proper functioning of this arrangement depends largely on making the ratio of the mean value of web tension to the restoring force of the oscillating support such that a mean deformation results from a mean web tension. When this condition is satisfied, a peak tension occurring in the web can effect further deformation of the support surface, producing a shortening of the web path, whereas a relaxation of web tension will cause a relaxation of the already existing deformation, the result being an elongation of the web path.

In view of the close approximation to inertia-free conditions, oscillations can be equalized which'include high frequencies of web-variation up to about 50 oscillations per second. The method of the invention is particularly suitable for oscillations in the range of about five to 30 per second. The oscillations may be observed by means of a stroboscope in the vicinity of the support, and the frequency can be easily read on a scale.

In addition to the equalization of longitudinal variations, the method of the invention also enables the equalization of oblique tensions and sagging in the web.

The width of the web to be equalized is not a critical factor for the method of the invention. Obviously, the width of the support should be at least equal to the width of the web. Equaliztion of a longitudinal variation is largely dependent upon the amount of deformation of the support and upon the length of the web section in contact with the support. Accordingly, if large length variations or tensile variations are to be equalized in the web, a larger support will be selected, a smaller support being suitable for samll longitudinal variations.

The invention further provides an apparatus for use in the method of the invention including a carrier of circular cross-section upon which is suspended, as a support for the web, a hollow cylindrical sleeve of internal diameter greater than the external diameter of the carrier, which sleeve is of resiliently flexible material and capable of being deformed by a running web looped around it.

The carrier may be a rotatable roller or rollers, or may be of rod-like nature. The resiliently flexible material for the hollow cylindrical support is deformable under pressure and may be spring steel or a strong plastic foil. The support may consist of one or more layers of thick plastic film, usually wound in a rectangular manner or in spiral form, or of a closed tubular cylinder. A combination of plastic film and thin spring steel strips also may be employed. The degree of resilience of the support need not be very great and depends on the mean tension prevailing in the web.

Another embodiment of the apparatus may include, likewise suspended upon the carrier and between it and the sleeve, one or more further sleeves, each sleeve being of greater internal diameter than the external diameter of the carrier or sleeve within it and the materials of the sleeves being such that all are resiliently deformable by a running web looped around the outer sleeve. The materials of the various sleeves may be the same or different.

The sleeve or sleeves either may be fixed or capable of moving in the web direction. Preferably the carrier and the sleeve 'or sleeves are each separate and rotatable. Rotation is preferably such as to give a surface speed equal to the speed of the web.

A still furher embodiment of the invention includes, as support for the web, a hollow cylindrical sleeve of resiliently flexible material whichis capable of being deformed by a web running over it, the sleeve being externally mounted on a pair of spaced rotatable rollers and a retaining member for the sleeve being mounted within it.

It is advisable to adapt the surface of the support to the properties of the web. Thus, in a rotatable support arrangement, it is of advantage to roughen the support surface, so as to increase the static friction. With a fixed support, on the other hand, the support suface should ensure minimum friction.

The apparatus of the invention is illustrated diagrammatically by way of example in the accompanying drawings in which:

FIG. 1 is a perspective view of one embodiment in the unstressed condition,

FIG. 2 is a similar view of the same embodiment in a stressed condition, also showing auxiliary rollers,

FIG. 3 is a similar view to FIG. 1 ofa second embodiment,

FIG. 4 is a perspective view of a third embodiment in a stressed condition,

FIG. 5 is a similar view to FIG. 1 with an adjacent winding roller, the embodiment of FIG. 1 being shown in the unstressed condition. FIG. 6 is also a perspective view, which shows the arrangement of FIG. 5 in operation with an auxiliary roller, and

FIG. 7 is an end elevation showing the principle of operation of the embodiment of FIGS. 1 and 2.

Referring to the drawings, in .FIG. 1 a roller 1 is mounted for free and/or positive rotation and/or for retention in a fixed position and carries a flexible cylindrical sleeve 2 which can be freely supported on the roller 1, or fixed to it when the roller is fixed, or canbe positively rotated independently of the roller 1. When unstressed, the sleeve 2'is circular, but when stressed by passage of a web around it, it can become deformed.

In FIG. 2 it is assumed that roller 1 and sleeve 2a are separate and both freely rotatable by passage of a web 6. Sleeve 2a is shown deformed into an oval shape under the web tension. In FIG. 2 also the web is shown guided by rollers 8 and 9 and the arrangement is such that the change of direction of the web around the deformed sleeve 2a is approximately 180.. The. operation could be conducted with larger or smaller web loop angles.

The embodiment of FIG. 3 includes a plurality of flexible sleeves 2, 3 and 3 of different diameters. The inner sleeves are of suitable flexibility relative to the outer sleeve 2. I

In FIG. 4 a flexible sleeve 2 is shown supported on two rollers 4, 5. In this case a member 7 is provided within the sleeve but its function is merely to prevent the sleeve 2 from being dislodged. This embodiment is especially suitable in the case of small looping angles of the web 6 because for this arrangement greater resilieht deformation of the sleeve can be achieved.

FIG. 5 illustrates a theoretical unstressed position of the main components of FIG. 6, showing, on a core, a web roll 10 of which the true shape is shown somewhat exaggerated in FIG; 6.

The arrangement of FIG. 6 is intended to run at high speeds. In FIG. 6, the deformed sleeve is given the numeral 11. It is in contact with the outer winding of the roll 10 produced by a web 12 and, by changing its degree of deformation, can follow the outline of the roll. The tension in the web 12 is thereby equalized. An auxiliary roller 13 prevents excessive lateral movement of the sleeve 11.

FIG. 7 shows in particular the variation of the length of the path of a web 6 due to deformation'of a sleeve 2. If it could be assumed, in the'first place, that the web 6 were not tensioned, the sleeve 2 would retain its circular section. The path of the web between points A and B would then be a maximum. At the other extreme, assuming maximum deformation of the sleeve 2, the web would take a path corresponding to the broken line 6', which is the minimum possible path between points A and B. Theoretically the degree of deformation of the sleeve 2 could vary between these limits. In practice a path approximately corresponding to the dotted line 6" would be selected, this line corresponding to the medium web tension.

The operation of the apparatus'according to the invention may be described as follows: the support 2 of resiliently flexible material wound in the form of a circle or consisting of a tube is pushed over the carrier 1,

which prevents the support 2 from sagging, but is also capable of following the rotational movement of the support. The roational speed of the two surfaces may be determined by the feed speed of the material web 6 passing over them. The resilience of the support 2 may .be adjusted by the number of wound layers or by the thickness of the material selected.

The web 6 is passed around the support 2 at a web loop angle, so that the support 2 is compressed and deformed under the action of the web tension and assumes a somewhat longer, approximately oval'shape. Due to its resilience, the support 2 has the tendency to revert to its original shape and thus exerts a force upon the web which should approximately correspond in the magnitude thereof to the tension present in the web. In the preferred embodiment described, the advancing material web is in engagement with the surface of the elastic support by means of the generated friction and thus ensures that the circumferential speed of the support 2 and the feed speed of the material web 6 are identical.

The advantages attainable by the invention are as follows:

As already has been mentioned, the width of-the web depends only upon the width of the carrier and that of the support. A particularly suitable working range comprises widths of from 0.01 to about 5 meters. Usually there is no limitation as to width if the carrier can be provided with adequate bending strength even. in large widths, without influencing the oscillating support by its own weight. Accordingly, the support can be adapted to low or high web tensions even with large web widths, without there being a risk of flexing over the width of the web. A further advantage attained by the invention is the fact that the masses of the individual or multiple supports which participate in the oscillation can be maintained very low, so that the system can be considered as largely inertia-free. A decisive difference between conventional apparatus and the apparatus of the invention is that, with the aid of the latter, web oscillation of very short phase also can be equalized. Thus, it is readily possible to equalize-oscillations at frequencies from l to 50 per second, provided that suitably selected material is used for the support.

It also should be noted that not only can longitudinal oscillations distributed over the entire width of the web be equalized, but also partial differences in the web can be elimated by varying degrees of deformation. Another substantial advantage is the fact that the method and apparatus of the invention can be employed at take-up or wind-off positions. A reliable solution therefore has been found to the problem of establishing the frequently desired permanent contact between the wound material and a take-up roll which may have become of irregular periphery. It should be remembered that, in many cases, the winding cores with rolls of wound web run somewhat out of true or are out of balance. or not entirely round. In the case of previously known apparatuses, a pendulum-type roller, for exam- 6 ple, would touch only the highest points of the roll and would be incapable, due to inertia, of contacting the wound roll over its entire periphery. The method of the present invention, on the other hand, ensures permanent contact at constantly defined pressure, even at high'running speeds, and thus makes for a far better structure of the wound roll. Even sensitive webs can be run at very low web tension and even sudden peak tensions will not destroy the web.

It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

What is claimed is: 1. An apparatus for straightguiding and simultaneously compensating for variations in length, especially short-phase variations in length, in the running of c a web under tension and arriving at the apparatus with cillation when a web is passed thereover are oscillated inphase between a cylindrical and an oval form relative to the arriving variations in length, and at least two deflector means for looping a web around said cylinder means. v 2. An apparatus as claimed in claim 1 comprising at least one additional hollow cylinder means of a flexible material between said carrier means and said hollow cylinder, the diameter of said additional hollow cylinder being greater than that of said carrier means and smaller than that of said hollow cylinder and said additional cylinder having a low inertia so that parts capable of oscillation by passage of a web over said hollow cylinder oscillate in phase with the arriving variations in length.

3. An apparatus as claimed in claim 1 including an auxilary roller for limiting movement of said hollow cylinder away from the surface of an adjacent roll.

4 An apparatus as claimed in claim l in which the carrier means is rotatable.

- 5. An apparatus for straight guiding and :simultaneously compensating for variations in length, es'pe-. cially short-phase variations in length, in the running of a web under tension and arriving at the apparatus with said variations in length, comprising at least one retain- 1 ing means,

a freely rotatable, flexible, hollow cylinder means surrounding said retaining means, said cylinder means having a diameter greater than that of said retaining means and a low inertia so that parts capable of oscillation when a web is passed thereover are oscillated in phase between a cylindrical and an oval form relative to the arriving variations in length, and a pair of spaced, external roller means for supporting said cylinder means.

I UNITED STATES PATENT OFFICE:- CERTIFICATE OF CORRECTION Patent No. 3,790,056 Dated February 5,- 1974 Inventor(s) Willi 1. Schmidt e1: a1

vIt is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Line 43 "auxilary" should read auxiliary Signed and sealed this 20th day of August 1974.

(SEAL) N Attestz' I R MCCQY M. GIBSON, IJR. C. MARSHALL-DAMN I Attesting Officer R Commissionerv of Patents Itemfig I "Kornelli" should read Korneli Column ijuhee 8 through 11 should be deleted. Line 55,

"equaliztion" should read equalization v Column 5, line 9, "Equallztion" should read Equalization Line 15, "samll" sh ould read small Column l line 40, "resilieht" should read resilient Column 5 li-ne 52 "elimated" should read aeliminated Column 6, line 24, "diamerter" should read diameter F po'wso 1 v Y I USCOMM-DC wan-pee. i U. S. GOYIINIENT PRINTING OFFICI II. 0-8ll-8Jl. 

1. An apparatus for straight guiding and simultaneously compensating for variations in length, especially short-phase variations in length, in the running of a web under tension and arriving at the apparatus with said variations in length, comprising at least one circular carrier means, a freely rotable, flexible, hollow cylinder means surrounding said carrier means, said cylinder means having a diamerter greater than that of said carrier means and a low inertia so that parts capable of oscillation when a web is passed thereover are oscillated in phase between a cylindrical and an oval form relative to the arriving variations in length, and at least two deflector means for looping a web around said cylinder means.
 2. An apparatus as claimed in claim 1 comprising at least one additional hollow cylinder means of a flexible material between said carrier means and said hollow cylinder, the diameter of said additional hollow cylinder being greater than thaT of said carrier means and smaller than that of said hollow cylinder and said additional cylinder having a low inertia so that parts capable of oscillation by passage of a web over said hollow cylinder oscillate in phase with the arriving variations in length.
 3. An apparatus as claimed in claim 1 including an auxilary roller for limiting movement of said hollow cylinder away from the surface of an adjacent roll. 4 . An apparatus as claimed in claim 1 in which the carrier means is rotatable.
 5. An apparatus for straight guiding and simultaneously compensating for variations in length, especially short-phase variations in length, in the running of a web under tension and arriving at the apparatus with said variations in length, comprising at least one retaining means, a freely rotatable, flexible, hollow cylinder means surrounding said retaining means, said cylinder means having a diameter greater than that of said retaining means and a low inertia so that parts capable of oscillation when a web is passed thereover are oscillated in phase between a cylindrical and an oval form relative to the arriving variations in length, and a pair of spaced, external roller means for supporting said cylinder means. 